Hackers targeted the software that developers use to create apps for Apple’s App store. In China, access to foreign websites can be spotty and slow. The hackers advertised a faster download for Apple’s development tool kit called Xcode that instead of being hosted on Apple’s official servers was on Baidu Inc.’s (BIDU) cloud service, which is widely used in the country and hosts very fast downloads.

The malicious version of the tool kit then compromised some of the most popular Apps in China including Tencent Holdings Ltd’s (TCEHY) WeChat, Tencent-baked Didi Dache, and a streaming music service from Netease and a train ticketing site.

“This is a significant compromise of Apple’s app store. Apple (AAPL) notoriously manually reviews all app submissions and, in comparison to Android stores, has been relatively malware-free. This is the most widespread and significant spread of malware in the history of the Apple app store, anywhere in the world,” said Greatfire.org, an activist site tracking China’s Internet firewall.

“Xcode is usually obtained directly from Apple’s Mac App Store, but because large cross-border downloads can be slow and unreliable in China, in large part because of the government’s Internet controls, many users there turn to potentially unsafe unofficial sources,” the China Digital times concluded.

And over the weekend companies had responded with updated versions of apps and Apple said it had removed the infected apps. Baidu had taken down the infected version of Xcode. Tencent said the hack didn’t expose users’ information.

China’s tight Internet controls appear to have backfired, for once very publicly, putting the country’s own tech champions at risk.